Toothpaste formulations have been recently developed that exhibit antibiotic properties. Such formulations inhibit the growth of plaque, and consequently the advent of gum disease. For example, formulations described in U.S. Pat. No. 4,627,974 containing monoalkyl and dialkyl ethers of dianhydrohexitols are said to be effective in reducing plaque accumulation caused by bacteria.
Currently, a commercially available toothpaste employs the organic compound triclosan as an antibiotic agent. Triclosan is believed to quickly kill relevant bacteria during normal toothbrushing and leave a residue which exhibits long-lasting antimicrobial activity.
However, triclosan is an organic compound, and therefore suffers from the disadvantage that antibiotic resistance can develop over time with continued use. Furthermore, triclosan is suspected of inducing skin irritation.
A number of metal ions have been shown to possess antibiotic activity, including silver, copper, zinc, mercury, tin, lead, bismutin, cadmium, chromium and thallium ions. These antibiotic metal ions are believed to exert their effects by disrupting respiration and electron transport systems upon absorption into bacterial or fungal cells. Antimicrobial metal ions of silver, gold, copper and zinc, in particular, are considered safe for in vivo use. Antimicrobial silver ions are particularly useful for in vivo use due to the fact that they are not substantially absorbed into the body.
These ions, however, cannot be practically employed in current toothpaste formulations because the formulations contain sulfates and phosphates that inactivate the antibiotic activity of the ions.
Antibiotic zeolites have been prepared by replacing all or part of the ion-exchangeable ions in zeolite with ammonium ions and antibiotic metal ions, as described in U.S. Pat. Nos. 4,938,958 and 4,911,898. Such zeolites have been incorporated in antibiotic resins (as shown in U.S. Pat. Nos. 4,938,955 and 4,906,464) and polymer articles (U.S. Pat. No. 4,775,585). Polymers including the antibiotic zeolites have been used to make refrigerators, dish washers, rice cookers, plastic film, chopping boards, vacuum bottles, plastic pails, and garbage containers. Other materials in which antibiotic zeolites have been incorporated include flooring, wall paper, cloth, paint, napkins, plastic automobile parts, catheters, bicycles, pens, toys, sand, and concrete. Examples of such uses are described in U.S. Pat. Nos. 5,714,445; 5,697,203; 5,562,872; 5,180,585; 5,714,430; and 5,102,401. These applications, however, involve slow release of antibiotic silver from the zeolite particles. In toothpaste formulations, on the other hand, the antibiotic action must be exerted very quickly, i.e, during the fifteen to thirty second duration of a normal toothbrushing.
There is therefore a need for an antibiotic toothpaste formulation that avoids use of organic compounds that can induce development of resistant bacterial strains.
There is also a need for a toothpaste formulation that leaves an effective antibiotic residue that continues to kill plaque-forming bacteria for a substantial period after application.